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Merry Christmas cactus

I can’t imagine any other plant that embodies the abundance and exuberant excess of the holidays quite like a Schlumbergera. Blithewold’s recently gifted Thanksgiving/Christmas cactus in particular maybe — though I did hear that it was a good year for Schlumbergera all around. My two at home bloomed their little arms off too – but not like this one. It’s been going non-stop since our first Friday Sparkle right after Thanksgiving and shows no signs of quitting. And every Friday, as it stops visitors in their tracks, they’ve asked me and Gail the age-old questions of why theirs isn’t blooming/why it does some years and not others/why one plant will bloom while another doesn’t?

We all know they are day-length sensitive, needing a period of darkness to set their buds. But this does not mean they should be locked in a closet for weeks at a time. Bad idea, actually, to deprive them of daylight altogether like that. Better to give them natural nights, at least 13 hours long, unpolluted by lamplight. (I use that advice as a good excuse to go to bed at a reasonable hour.)

They also need cool nights in combination with long ones and that right there might be why some refuse to bloom. As soon as we turn the heat on in the house — unless we program the thermostat for night dips into the 50s — our modern, efficient, weather-sealed houses may be too evenly modulated to toggle the temperature trigger. Leaving plants outside at least until the forecast threatens dips into the 40s will probably give them the requisite weeks of cool, dark nights.

Although my favorite tropical plant reference book, the weighty Exotica by A. F. Graf, recommends temperatures that swing only down into the low 60s, we have used this Christmas cactus to decorate the “cold” end greenhouse where night temps dip into the 40s, and I would bet that’s partly why it has held its blooms so long. As if its been preserved in the refrigerator. By contrast, my plants at home, after the first and fast glorious bloom, dropped most of their follow-up buds. It could be they’re too warm but also maybe too wet. Although the soil shouldn’t be allowed to completely dry out, it shouldn’t stay overly moist either, especially through the winter.

The schlumbergera’s popularity among even non-gardeners belies their evident finickiness and difficulty as houseplants. If they didn’t bloom more often than not and survive for years to outgrow their holiday pedestals and mantels, they wouldn’t have become the passalong favorites that they are.

Can you count on yours to bloom for the holidays? Does it stay in bloom for ages too — or at least for the 12 days of Christmas? What’s your secret of success?